java/util/NavigableMap.java

/*
 * Written by Doug Lea with assistance from members of JCP JSR-166
 * Expert Group and released to the public domain, as explained at
 * http://creativecommons.org/licenses/publicdomain
 */

package java.util;
import java.util.*; // for javadoc (till 6280605 is fixed)

/**
 * A {@link SortedMap} extended with navigation methods returning the
 * closest matches for given search targets. Methods
 * <tt>lowerEntry</tt>, <tt>floorEntry</tt>, <tt>ceilingEntry</tt>,
 * and <tt>higherEntry</tt> return <tt>Map.Entry</tt> objects
 * associated with keys respectively less than, less than or equal,
 * greater than or equal, and greater than a given key, returning
 * <tt>null</tt> if there is no such key.  Similarly, methods
 * <tt>lowerKey</tt>, <tt>floorKey</tt>, <tt>ceilingKey</tt>, and
 * <tt>higherKey</tt> return only the associated keys. All of these
 * methods are designed for locating, not traversing entries.
 *
 * <p>A <tt>NavigableMap</tt> may be viewed and traversed in either
 * ascending or descending key order.  The <tt>Map</tt> methods
 * <tt>keySet</tt> and <tt>entrySet</tt> return ascending views, and
 * the additional methods <tt>descendingKeySet</tt> and
 * <tt>descendingEntrySet</tt> return descending views. The
 * performance of ascending traversals is likely to be faster than
 * descending traversals.  Notice that it is possible to perform
 * subrange traversals in either direction using <tt>navigableSubMap</tt>.
 * Methods <tt>navigableSubMap</tt>, <tt>navigableHeadMap</tt>, and
 * <tt>navigableTailMap</tt> differ from the similarly named
 * <tt>SortedMap</tt> methods only in their declared return types.
 * Submaps of any <tt>NavigableMap<tt> must implement the
 * <tt>NavigableMap</tt> interface.
 *
 * <p>This interface additionally defines methods <tt>firstEntry</tt>,
 * <tt>pollFirstEntry</tt>, <tt>lastEntry</tt>, and
 * <tt>pollLastEntry</tt> that return and/or remove the least and
 * greatest mappings, if any exist, else returning <tt>null</tt>.
 *
 * <p> Implementations of entry-returning methods are expected to
 * return <tt>Map.Entry</tt> pairs representing snapshots of mappings
 * at the time they were produced, and thus generally do <em>not</em>
 * support the optional <tt>Entry.setValue</tt> method. Note however
 * that it is possible to change mappings in the associated map using
 * method <tt>put</tt>.
 *
 * <p>This interface is a member of the
 * <a href="{@docRoot}/../guide/collections/index.html">
 * Java Collections Framework</a>.
 *
 * @author Doug Lea
 * @param <K> the type of keys maintained by this map
 * @param <V> the type of mapped values
 * @since 1.6
 */
public interface NavigableMap<K,V> extends SortedMap<K,V> {
    /**
     * Returns a key-value mapping associated with the greatest key
     * strictly less than the given key, or <tt>null</tt> if there is
     * no such key.
     *
     * @param key the key
     * @return an entry with the greatest key less than <tt>key</tt>,
     *         or <tt>null</tt> if there is no such key
     * @throws ClassCastException if the specified key cannot be compared
     *         with the keys currently in the map
     * @throws NullPointerException if the specified key is null
     *         and this map does not permit null keys
     */
    Map.Entry<K,V> lowerEntry(K key);

    /**
     * Returns the greatest key strictly less than the given key, or
     * <tt>null</tt> if there is no such key.
     *
     * @param key the key
     * @return the greatest key less than <tt>key</tt>,
     *         or <tt>null</tt> if there is no such key
     * @throws ClassCastException if the specified key cannot be compared
     *         with the keys currently in the map
     * @throws NullPointerException if the specified key is null
     *         and this map does not permit null keys
     */
    K lowerKey(K key);

    /**
     * Returns a key-value mapping associated with the greatest key
     * less than or equal to the given key, or <tt>null</tt> if there
     * is no such key.
     *
     * @param key the key
     * @return an entry with the greatest key less than or equal to
     *         <tt>key</tt>, or <tt>null</tt> if there is no such key
     * @throws ClassCastException if the specified key cannot be compared
     *         with the keys currently in the map
     * @throws NullPointerException if the specified key is null
     *         and this map does not permit null keys
     */
    Map.Entry<K,V> floorEntry(K key);

    /**
     * Returns the greatest key less than or equal to the given key,
     * or <tt>null</tt> if there is no such key.
     *
     * @param key the key
     * @return the greatest key less than or equal to <tt>key</tt>,
     *         or <tt>null</tt> if there is no such key
     * @throws ClassCastException if the specified key cannot be compared
     *         with the keys currently in the map
     * @throws NullPointerException if the specified key is null
     *         and this map does not permit null keys
     */
    K floorKey(K key);

    /**
     * Returns a key-value mapping associated with the least key
     * greater than or equal to the given key, or <tt>null</tt> if
     * there is no such key.
     *
     * @param key the key
     * @return an entry with the least key greater than or equal to
     *         <tt>key</tt>, or <tt>null</tt> if there is no such key
     * @throws ClassCastException if the specified key cannot be compared
     *         with the keys currently in the map
     * @throws NullPointerException if the specified key is null
     *         and this map does not permit null keys
     */
    Map.Entry<K,V> ceilingEntry(K key);

    /**
     * Returns the least key greater than or equal to the given key,
     * or <tt>null</tt> if there is no such key.
     *
     * @param key the key
     * @return the least key greater than or equal to <tt>key</tt>,
     *         or <tt>null</tt> if there is no such key
     * @throws ClassCastException if the specified key cannot be compared
     *         with the keys currently in the map
     * @throws NullPointerException if the specified key is null
     *         and this map does not permit null keys
     */
    K ceilingKey(K key);

    /**
     * Returns a key-value mapping associated with the least key
     * strictly greater than the given key, or <tt>null</tt> if there
     * is no such key.
     *
     * @param key the key
     * @return an entry with the least key greater than <tt>key</tt>,
     *         or <tt>null</tt> if there is no such key
     * @throws ClassCastException if the specified key cannot be compared
     *         with the keys currently in the map
     * @throws NullPointerException if the specified key is null
     *         and this map does not permit null keys
     */
    Map.Entry<K,V> higherEntry(K key);

    /**
     * Returns the least key strictly greater than the given key, or
     * <tt>null</tt> if there is no such key.
     *
     * @param key the key
     * @return the least key greater than <tt>key</tt>,
     *         or <tt>null</tt> if there is no such key
     * @throws ClassCastException if the specified key cannot be compared
     *         with the keys currently in the map
     * @throws NullPointerException if the specified key is null
     *         and this map does not permit null keys
     */
    K higherKey(K key);

    /**
     * Returns a key-value mapping associated with the least
     * key in this map, or <tt>null</tt> if the map is empty.
     *
     * @return an entry with the least key,
     *         or <tt>null</tt> if this map is empty
     */
    Map.Entry<K,V> firstEntry();

    /**
     * Returns a key-value mapping associated with the greatest
     * key in this map, or <tt>null</tt> if the map is empty.
     *
     * @return an entry with the greatest key,
     *         or <tt>null</tt> if this map is empty
     */
    Map.Entry<K,V> lastEntry();

    /**
     * Removes and returns a key-value mapping associated with
     * the least key in this map, or <tt>null</tt> if the map is empty.
     *
     * @return the removed first entry of this map,
     *         or <tt>null</tt> if this map is empty
     */
    Map.Entry<K,V> pollFirstEntry();

    /**
     * Removes and returns a key-value mapping associated with
     * the greatest key in this map, or <tt>null</tt> if the map is empty.
     *
     * @return the removed last entry of this map,
     *         or <tt>null</tt> if this map is empty
     */
    Map.Entry<K,V> pollLastEntry();

    /**
     * Returns a {@link Set} view of the keys contained in this map.
     * The set's iterator returns the keys in descending order.
     * The set is backed by the map, so changes to the map are
     * reflected in the set, and vice-versa.  If the map is modified
     * while an iteration over the set is in progress (except through
     * the iterator's own <tt>remove</tt> operation), the results of
     * the iteration are undefined.  The set supports element removal,
     * which removes the corresponding mapping from the map, via the
     * <tt>Iterator.remove</tt>, <tt>Set.remove</tt>,
     * <tt>removeAll</tt>, <tt>retainAll</tt>, and <tt>clear</tt>
     * operations.  It does not support the <tt>add</tt> or <tt>addAll</tt>
     * operations.
     *
     * @return a set view of the keys contained in this map, sorted in
     *         descending order
     */
    Set<K> descendingKeySet();

    /**
     * Returns a {@link Set} view of the mappings contained in this map.
     * The set's iterator returns the entries in descending key order.
     * The set is backed by the map, so changes to the map are
     * reflected in the set, and vice-versa.  If the map is modified
     * while an iteration over the set is in progress (except through
     * the iterator's own <tt>remove</tt> operation, or through the
     * <tt>setValue</tt> operation on a map entry returned by the
     * iterator) the results of the iteration are undefined.  The set
     * supports element removal, which removes the corresponding
     * mapping from the map, via the <tt>Iterator.remove</tt>,
     * <tt>Set.remove</tt>, <tt>removeAll</tt>, <tt>retainAll</tt> and
     * <tt>clear</tt> operations.  It does not support the
     * <tt>add</tt> or <tt>addAll</tt> operations.
     *
     * @return a set view of the mappings contained in this map,
     *         sorted in descending key order
     */
    Set<Map.Entry<K, V>> descendingEntrySet();

    /**
     * Returns a view of the portion of this map whose keys range from
     * <tt>fromKey</tt>, inclusive, to <tt>toKey</tt>, exclusive.  (If
     * <tt>fromKey</tt> and <tt>toKey</tt> are equal, the returned map
     * is empty.)  The returned map is backed by this map, so changes
     * in the returned map are reflected in this map, and vice-versa.
     * The returned map supports all optional map operations that this
     * map supports.
     *
     * <p>The returned map will throw an <tt>IllegalArgumentException</tt>
     * on an attempt to insert a key outside its range.
     *
     * @param fromKey low endpoint (inclusive) of the keys in the returned map
     * @param toKey high endpoint (exclusive) of the keys in the returned map
     * @return a view of the portion of this map whose keys range from
     *         <tt>fromKey</tt>, inclusive, to <tt>toKey</tt>, exclusive
     * @throws ClassCastException if <tt>fromKey</tt> and <tt>toKey</tt>
     *         cannot be compared to one another using this map's comparator
     *         (or, if the map has no comparator, using natural ordering).
     *         Implementations may, but are not required to, throw this
     *         exception if <tt>fromKey</tt> or <tt>toKey</tt>
     *         cannot be compared to keys currently in the map.
     * @throws NullPointerException if <tt>fromKey</tt> or <tt>toKey</tt>
     *         is null and this map does not permit null keys
     * @throws IllegalArgumentException if <tt>fromKey</tt> is greater than
     *         <tt>toKey</tt>; or if this map itself has a restricted
     *         range, and <tt>fromKey</tt> or <tt>toKey</tt> lies
     *         outside the bounds of the range
     */
    NavigableMap<K,V> navigableSubMap(K fromKey, K toKey);

    /**
     * Returns a view of the portion of this map whose keys are
     * strictly less than <tt>toKey</tt>.  The returned map is backed
     * by this map, so changes in the returned map are reflected in
     * this map, and vice-versa.  The returned map supports all
     * optional map operations that this map supports.
     *
     * <p>The returned map will throw an <tt>IllegalArgumentException</tt>
     * on an attempt to insert a key outside its range.
     *
     * @param toKey high endpoint (exclusive) of the keys in the returned map
     * @return a view of the portion of this map whose keys are strictly
     *         less than <tt>toKey</tt>
     * @throws ClassCastException if <tt>toKey</tt> is not compatible
     *         with this map's comparator (or, if the map has no comparator,
     *         if <tt>toKey</tt> does not implement {@link Comparable}).
     *         Implementations may, but are not required to, throw this
     *         exception if <tt>toKey</tt> cannot be compared to keys
     *         currently in the map.
     * @throws NullPointerException if <tt>toKey</tt> is null
     *         and this map does not permit null keys
     * @throws IllegalArgumentException if this map itself has a
     *         restricted range, and <tt>toKey</tt> lies outside the
     *         bounds of the range
     */
    NavigableMap<K,V> navigableHeadMap(K toKey);

    /**
     * Returns a view of the portion of this map whose keys are
     * greater than or equal to <tt>fromKey</tt>.  The returned map is
     * backed by this map, so changes in the returned map are
     * reflected in this map, and vice-versa.  The returned map
     * supports all optional map operations that this map supports.
     *
     * <p>The returned map will throw an <tt>IllegalArgumentException</tt>
     * on an attempt to insert a key outside its range.
     *
     * @param fromKey low endpoint (inclusive) of the keys in the returned map
     * @return a view of the portion of this map whose keys are greater
     *         than or equal to <tt>fromKey</tt>
     * @throws ClassCastException if <tt>fromKey</tt> is not compatible
     *         with this map's comparator (or, if the map has no comparator,
     *         if <tt>fromKey</tt> does not implement {@link Comparable}).
     *         Implementations may, but are not required to, throw this
     *         exception if <tt>fromKey</tt> cannot be compared to keys
     *         currently in the map.
     * @throws NullPointerException if <tt>fromKey</tt> is null
     *         and this map does not permit null keys
     * @throws IllegalArgumentException if this map itself has a
     *         restricted range, and <tt>fromKey</tt> lies outside the
     *         bounds of the range
     */
    NavigableMap<K,V> navigableTailMap(K fromKey);
}
Revision:	1.11
Committed:	Wed Jul 20 02:18:52 2005 UTC (18 years, 9 months ago) by jsr166
Branch:	MAIN
Changes since 1.10:	+3 -2 lines
Log Message:	doc fixes
#	User	Rev	Content
1	dl	1.1	/*
2			* Written by Doug Lea with assistance from members of JCP JSR-166
3			* Expert Group and released to the public domain, as explained at
4			* http://creativecommons.org/licenses/publicdomain
5			*/
6
7			package java.util;
8	jsr166	1.11	import java.util.*; // for javadoc (till 6280605 is fixed)
9	dl	1.1
10			/**
11			* A {@link SortedMap} extended with navigation methods returning the
12			* closest matches for given search targets. Methods
13			* <tt>lowerEntry</tt>, <tt>floorEntry</tt>, <tt>ceilingEntry</tt>,
14			* and <tt>higherEntry</tt> return <tt>Map.Entry</tt> objects
15			* associated with keys respectively less than, less than or equal,
16			* greater than or equal, and greater than a given key, returning
17			* <tt>null</tt> if there is no such key. Similarly, methods
18			* <tt>lowerKey</tt>, <tt>floorKey</tt>, <tt>ceilingKey</tt>, and
19			* <tt>higherKey</tt> return only the associated keys. All of these
20			* methods are designed for locating, not traversing entries.
21			*
22			* <p>A <tt>NavigableMap</tt> may be viewed and traversed in either
23			* ascending or descending key order. The <tt>Map</tt> methods
24			* <tt>keySet</tt> and <tt>entrySet</tt> return ascending views, and
25			* the additional methods <tt>descendingKeySet</tt> and
26			* <tt>descendingEntrySet</tt> return descending views. The
27			* performance of ascending traversals is likely to be faster than
28			* descending traversals. Notice that it is possible to perform
29	dl	1.4	* subrange traversals in either direction using <tt>navigableSubMap</tt>.
30			* Methods <tt>navigableSubMap</tt>, <tt>navigableHeadMap</tt>, and
31			* <tt>navigableTailMap</tt> differ from the similarly named
32	dl	1.10	* <tt>SortedMap</tt> methods only in their declared return types.
33	jsr166	1.11	* Submaps of any <tt>NavigableMap<tt> must implement the
34			* <tt>NavigableMap</tt> interface.
35	jsr166	1.5	*
36	dl	1.1	* <p>This interface additionally defines methods <tt>firstEntry</tt>,
37			* <tt>pollFirstEntry</tt>, <tt>lastEntry</tt>, and
38			* <tt>pollLastEntry</tt> that return and/or remove the least and
39			* greatest mappings, if any exist, else returning <tt>null</tt>.
40			*
41			* <p> Implementations of entry-returning methods are expected to
42			* return <tt>Map.Entry</tt> pairs representing snapshots of mappings
43			* at the time they were produced, and thus generally do <em>not</em>
44			* support the optional <tt>Entry.setValue</tt> method. Note however
45			* that it is possible to change mappings in the associated map using
46			* method <tt>put</tt>.
47			*
48	jsr166	1.7	* <p>This interface is a member of the
49			* <a href="{@docRoot}/../guide/collections/index.html">
50			* Java Collections Framework</a>.
51			*
52	dl	1.1	* @author Doug Lea
53			* @param <K> the type of keys maintained by this map
54	jsr166	1.5	* @param <V> the type of mapped values
55	jsr166	1.6	* @since 1.6
56	dl	1.1	*/
57			public interface NavigableMap<K,V> extends SortedMap<K,V> {
58			/**
59	jsr166	1.8	* Returns a key-value mapping associated with the greatest key
60			* strictly less than the given key, or <tt>null</tt> if there is
61			* no such key.
62	jsr166	1.5	*
63	jsr166	1.8	* @param key the key
64			* @return an entry with the greatest key less than <tt>key</tt>,
65			* or <tt>null</tt> if there is no such key
66			* @throws ClassCastException if the specified key cannot be compared
67			* with the keys currently in the map
68			* @throws NullPointerException if the specified key is null
69			* and this map does not permit null keys
70	dl	1.1	*/
71	jsr166	1.8	Map.Entry<K,V> lowerEntry(K key);
72	dl	1.1
73			/**
74	jsr166	1.8	* Returns the greatest key strictly less than the given key, or
75	dl	1.1	* <tt>null</tt> if there is no such key.
76	jsr166	1.5	*
77	jsr166	1.8	* @param key the key
78			* @return the greatest key less than <tt>key</tt>,
79			* or <tt>null</tt> if there is no such key
80			* @throws ClassCastException if the specified key cannot be compared
81			* with the keys currently in the map
82			* @throws NullPointerException if the specified key is null
83			* and this map does not permit null keys
84	dl	1.1	*/
85	jsr166	1.8	K lowerKey(K key);
86	dl	1.1
87			/**
88	jsr166	1.8	* Returns a key-value mapping associated with the greatest key
89			* less than or equal to the given key, or <tt>null</tt> if there
90			* is no such key.
91	jsr166	1.5	*
92	jsr166	1.8	* @param key the key
93			* @return an entry with the greatest key less than or equal to
94			* <tt>key</tt>, or <tt>null</tt> if there is no such key
95			* @throws ClassCastException if the specified key cannot be compared
96			* with the keys currently in the map
97			* @throws NullPointerException if the specified key is null
98			* and this map does not permit null keys
99	dl	1.1	*/
100	jsr166	1.8	Map.Entry<K,V> floorEntry(K key);
101	dl	1.1
102			/**
103	jsr166	1.8	* Returns the greatest key less than or equal to the given key,
104			* or <tt>null</tt> if there is no such key.
105	jsr166	1.5	*
106	jsr166	1.8	* @param key the key
107			* @return the greatest key less than or equal to <tt>key</tt>,
108			* or <tt>null</tt> if there is no such key
109			* @throws ClassCastException if the specified key cannot be compared
110			* with the keys currently in the map
111			* @throws NullPointerException if the specified key is null
112			* and this map does not permit null keys
113	dl	1.1	*/
114	jsr166	1.8	K floorKey(K key);
115	dl	1.1
116			/**
117	jsr166	1.8	* Returns a key-value mapping associated with the least key
118			* greater than or equal to the given key, or <tt>null</tt> if
119			* there is no such key.
120	jsr166	1.5	*
121	jsr166	1.8	* @param key the key
122			* @return an entry with the least key greater than or equal to
123			* <tt>key</tt>, or <tt>null</tt> if there is no such key
124			* @throws ClassCastException if the specified key cannot be compared
125			* with the keys currently in the map
126			* @throws NullPointerException if the specified key is null
127			* and this map does not permit null keys
128	dl	1.1	*/
129	jsr166	1.8	Map.Entry<K,V> ceilingEntry(K key);
130	dl	1.1
131			/**
132	jsr166	1.8	* Returns the least key greater than or equal to the given key,
133			* or <tt>null</tt> if there is no such key.
134	jsr166	1.5	*
135	jsr166	1.8	* @param key the key
136			* @return the least key greater than or equal to <tt>key</tt>,
137			* or <tt>null</tt> if there is no such key
138			* @throws ClassCastException if the specified key cannot be compared
139			* with the keys currently in the map
140			* @throws NullPointerException if the specified key is null
141			* and this map does not permit null keys
142	dl	1.1	*/
143	jsr166	1.8	K ceilingKey(K key);
144	dl	1.1
145			/**
146			* Returns a key-value mapping associated with the least key
147			* strictly greater than the given key, or <tt>null</tt> if there
148	jsr166	1.8	* is no such key.
149	jsr166	1.5	*
150	jsr166	1.8	* @param key the key
151			* @return an entry with the least key greater than <tt>key</tt>,
152			* or <tt>null</tt> if there is no such key
153			* @throws ClassCastException if the specified key cannot be compared
154			* with the keys currently in the map
155			* @throws NullPointerException if the specified key is null
156			* and this map does not permit null keys
157	dl	1.1	*/
158	dl	1.3	Map.Entry<K,V> higherEntry(K key);
159	dl	1.1
160			/**
161			* Returns the least key strictly greater than the given key, or
162			* <tt>null</tt> if there is no such key.
163	jsr166	1.5	*
164	jsr166	1.8	* @param key the key
165			* @return the least key greater than <tt>key</tt>,
166			* or <tt>null</tt> if there is no such key
167			* @throws ClassCastException if the specified key cannot be compared
168			* with the keys currently in the map
169			* @throws NullPointerException if the specified key is null
170			* and this map does not permit null keys
171	dl	1.1	*/
172	dl	1.3	K higherKey(K key);
173	dl	1.1
174			/**
175			* Returns a key-value mapping associated with the least
176			* key in this map, or <tt>null</tt> if the map is empty.
177	jsr166	1.5	*
178	jsr166	1.8	* @return an entry with the least key,
179			* or <tt>null</tt> if this map is empty
180	dl	1.1	*/
181	dl	1.3	Map.Entry<K,V> firstEntry();
182	dl	1.1
183			/**
184			* Returns a key-value mapping associated with the greatest
185			* key in this map, or <tt>null</tt> if the map is empty.
186	jsr166	1.5	*
187	jsr166	1.8	* @return an entry with the greatest key,
188			* or <tt>null</tt> if this map is empty
189	dl	1.1	*/
190	dl	1.3	Map.Entry<K,V> lastEntry();
191	dl	1.1
192			/**
193			* Removes and returns a key-value mapping associated with
194			* the least key in this map, or <tt>null</tt> if the map is empty.
195	jsr166	1.5	*
196	jsr166	1.8	* @return the removed first entry of this map,
197			* or <tt>null</tt> if this map is empty
198	dl	1.1	*/
199	dl	1.3	Map.Entry<K,V> pollFirstEntry();
200	dl	1.1
201			/**
202			* Removes and returns a key-value mapping associated with
203			* the greatest key in this map, or <tt>null</tt> if the map is empty.
204	jsr166	1.5	*
205	jsr166	1.8	* @return the removed last entry of this map,
206			* or <tt>null</tt> if this map is empty
207	dl	1.1	*/
208	dl	1.3	Map.Entry<K,V> pollLastEntry();
209	dl	1.1
210			/**
211	jsr166	1.8	* Returns a {@link Set} view of the keys contained in this map.
212			* The set's iterator returns the keys in descending order.
213			* The set is backed by the map, so changes to the map are
214			* reflected in the set, and vice-versa. If the map is modified
215			* while an iteration over the set is in progress (except through
216			* the iterator's own <tt>remove</tt> operation), the results of
217			* the iteration are undefined. The set supports element removal,
218			* which removes the corresponding mapping from the map, via the
219			* <tt>Iterator.remove</tt>, <tt>Set.remove</tt>,
220	jsr166	1.9	* <tt>removeAll</tt>, <tt>retainAll</tt>, and <tt>clear</tt>
221			* operations. It does not support the <tt>add</tt> or <tt>addAll</tt>
222	dl	1.1	* operations.
223			*
224	jsr166	1.8	* @return a set view of the keys contained in this map, sorted in
225			* descending order
226	dl	1.1	*/
227			Set<K> descendingKeySet();
228
229			/**
230	jsr166	1.8	* Returns a {@link Set} view of the mappings contained in this map.
231			* The set's iterator returns the entries in descending key order.
232			* The set is backed by the map, so changes to the map are
233			* reflected in the set, and vice-versa. If the map is modified
234			* while an iteration over the set is in progress (except through
235			* the iterator's own <tt>remove</tt> operation, or through the
236			* <tt>setValue</tt> operation on a map entry returned by the
237			* iterator) the results of the iteration are undefined. The set
238			* supports element removal, which removes the corresponding
239			* mapping from the map, via the <tt>Iterator.remove</tt>,
240			* <tt>Set.remove</tt>, <tt>removeAll</tt>, <tt>retainAll</tt> and
241			* <tt>clear</tt> operations. It does not support the
242			* <tt>add</tt> or <tt>addAll</tt> operations.
243	dl	1.1	*
244	jsr166	1.8	* @return a set view of the mappings contained in this map,
245			* sorted in descending key order
246	dl	1.1	*/
247			Set<Map.Entry<K, V>> descendingEntrySet();
248
249			/**
250			* Returns a view of the portion of this map whose keys range from
251			* <tt>fromKey</tt>, inclusive, to <tt>toKey</tt>, exclusive. (If
252	jsr166	1.8	* <tt>fromKey</tt> and <tt>toKey</tt> are equal, the returned map
253			* is empty.) The returned map is backed by this map, so changes
254			* in the returned map are reflected in this map, and vice-versa.
255			* The returned map supports all optional map operations that this
256			* map supports.
257	dl	1.3	*
258	jsr166	1.8	* <p>The returned map will throw an <tt>IllegalArgumentException</tt>
259			* on an attempt to insert a key outside its range.
260	dl	1.1	*
261	jsr166	1.8	* @param fromKey low endpoint (inclusive) of the keys in the returned map
262			* @param toKey high endpoint (exclusive) of the keys in the returned map
263	dl	1.1	* @return a view of the portion of this map whose keys range from
264	jsr166	1.8	* <tt>fromKey</tt>, inclusive, to <tt>toKey</tt>, exclusive
265			* @throws ClassCastException if <tt>fromKey</tt> and <tt>toKey</tt>
266			* cannot be compared to one another using this map's comparator
267			* (or, if the map has no comparator, using natural ordering).
268			* Implementations may, but are not required to, throw this
269			* exception if <tt>fromKey</tt> or <tt>toKey</tt>
270			* cannot be compared to keys currently in the map.
271			* @throws NullPointerException if <tt>fromKey</tt> or <tt>toKey</tt>
272			* is null and this map does not permit null keys
273			* @throws IllegalArgumentException if <tt>fromKey</tt> is greater than
274			* <tt>toKey</tt>; or if this map itself has a restricted
275			* range, and <tt>fromKey</tt> or <tt>toKey</tt> lies
276			* outside the bounds of the range
277	dl	1.1	*/
278	dl	1.3	NavigableMap<K,V> navigableSubMap(K fromKey, K toKey);
279	dl	1.1
280			/**
281	jsr166	1.8	* Returns a view of the portion of this map whose keys are
282			* strictly less than <tt>toKey</tt>. The returned map is backed
283			* by this map, so changes in the returned map are reflected in
284			* this map, and vice-versa. The returned map supports all
285			* optional map operations that this map supports.
286			*
287			* <p>The returned map will throw an <tt>IllegalArgumentException</tt>
288			* on an attempt to insert a key outside its range.
289			*
290			* @param toKey high endpoint (exclusive) of the keys in the returned map
291	dl	1.1	* @return a view of the portion of this map whose keys are strictly
292	jsr166	1.8	* less than <tt>toKey</tt>
293	dl	1.1	* @throws ClassCastException if <tt>toKey</tt> is not compatible
294			* with this map's comparator (or, if the map has no comparator,
295	jsr166	1.8	* if <tt>toKey</tt> does not implement {@link Comparable}).
296			* Implementations may, but are not required to, throw this
297			* exception if <tt>toKey</tt> cannot be compared to keys
298			* currently in the map.
299			* @throws NullPointerException if <tt>toKey</tt> is null
300			* and this map does not permit null keys
301			* @throws IllegalArgumentException if this map itself has a
302			* restricted range, and <tt>toKey</tt> lies outside the
303			* bounds of the range
304	dl	1.1	*/
305	dl	1.3	NavigableMap<K,V> navigableHeadMap(K toKey);
306	dl	1.1
307			/**
308			* Returns a view of the portion of this map whose keys are
309	jsr166	1.8	* greater than or equal to <tt>fromKey</tt>. The returned map is
310			* backed by this map, so changes in the returned map are
311			* reflected in this map, and vice-versa. The returned map
312			* supports all optional map operations that this map supports.
313			*
314			* <p>The returned map will throw an <tt>IllegalArgumentException</tt>
315			* on an attempt to insert a key outside its range.
316			*
317			* @param fromKey low endpoint (inclusive) of the keys in the returned map
318	dl	1.1	* @return a view of the portion of this map whose keys are greater
319	jsr166	1.8	* than or equal to <tt>fromKey</tt>
320	dl	1.1	* @throws ClassCastException if <tt>fromKey</tt> is not compatible
321			* with this map's comparator (or, if the map has no comparator,
322	jsr166	1.8	* if <tt>fromKey</tt> does not implement {@link Comparable}).
323			* Implementations may, but are not required to, throw this
324			* exception if <tt>fromKey</tt> cannot be compared to keys
325			* currently in the map.
326			* @throws NullPointerException if <tt>fromKey</tt> is null
327			* and this map does not permit null keys
328			* @throws IllegalArgumentException if this map itself has a
329			* restricted range, and <tt>fromKey</tt> lies outside the
330			* bounds of the range
331	dl	1.1	*/
332	jsr166	1.8	NavigableMap<K,V> navigableTailMap(K fromKey);
333	dl	1.1	}